Jpeg压缩的两种方法

方法1：

procedure TForm1.Button2Click(Sender: TObject);
var
  JPEGImage: TJPEGImage;
begin
  if SavePictureDialog1.InitialDir =''then
      SavePictureDialog1.InitialDir := ExtractFilePath(OpenPictureDialog1.FileName);
  if trim(LabeledEdit1.Text) <>''then
      SavePictureDialog1.FileName := trim(LabeledEdit1.Text) +'.jpg ';
  if SavePictureDialog1.execute then
  begin
      JPEGImage := TJPEGImage.Create;
      JPEGImage.Assign(image1.Picture.Graphic);
      JPEGImage.CompressionQuality:=25;
      JPEGImage.Compress;
      JPEGImage.SaveToFile(ExtractFilePath(SavePictureDialog1.Filename)
        + trim(LabeledEdit1.Text) +'.jpg ');
  end;
end;

方法2：

procedure Tf_NewsPic.BitBtn1Click(Sender: TObject);
var
  i: Integer;
  JI: TJPEGImage;
begin
  if not OpenPictureDialog1.Execute then exit;
  for i :=0 to OpenPictureDialog1.Files.Count -1 do
  begin
    JI := TJPEGImage.Create;
    JI.LoadFromFile(OpenPictureDialog1.Files[i]);
    image4.Picture.Bitmap.Assign(JI);
    JI.Assign(image4.Picture.Bitmap);
    JI.CompressionQuality :=25;
    JI.Compress;
    JI.SaveToFile(zhtier.GetTempDir + ExtractFileName(OpenPictureDialog1.Files[i]));
    Q1.Append;
    TBlobField(Q1.Fieldbyname('图片')).LoadFromFile(OpenPictureDialog1.Files[i]);
    Q1.Post;
    JI.Free;
  end;
  Q1.Last;
end;

一般情况下，采用方法2来操作。压缩效果，可去华军软件园或天空下载站下载“图片伴侣”来体验下。